Tuesday, March 27, 2012

This document describes how to install a PureFTPd server that uses virtual users from a MySQL database instead of real system users. This is much more performant and allows to have thousands of ftp users on a single machine. In addition to that I will show the use of quota and upload/download bandwidth limits with this setup. Passwords will be stored encrypted as MD5 strings in the database.
For the administration of the MySQL database you can use web based tools like phpMyAdmin which will also be installed in this howto. phpMyAdmin is a comfortable graphical interface which means you do not have to mess around with the command line.
This tutorial is based on CentOS 6.2. You should already have set up a basic CentOS 6.2 system, for example as described in the first six chapters of this tutorial: The Perfect Server - CentOS 6.2 x86_64 With Apache2 [ISPConfig 3]
This howto is meant as a practical guide; it does not cover the theoretical backgrounds. They are treated in a lot of other documents in the web.
This document comes without warranty of any kind! I want to say that this is not the only way of setting up such a system. There are many ways of achieving this goal but this is the way I take. I do not issue any guarantee that this will work for you!

1 Preliminary Note

In this tutorial I use the hostname server1.example.com with the IP address 192.168.0.100. These settings might differ for you, so you have to replace them where appropriate.

2 Install MySQL And phpMyAdmin

First we enable the EPEL repository on our CentOS system as some packages that we are going to install in the course of this tutorial are not available in the official CentOS 6.2 repositories:

# phpMyAdmin - Web based MySQL browser written in php
#
# Allows only localhost by default
#
# But allowing phpMyAdmin to anyone other than localhost should be considered
# dangerous unless properly secured by SSL
Alias /phpMyAdmin /usr/share/phpMyAdmin
Alias /phpmyadmin /usr/share/phpMyAdmin
#
# Order Deny,Allow
# Deny from All
# Allow from 127.0.0.1
# Allow from ::1
#
Order Deny,Allow
Deny from All
Allow from 127.0.0.1
Allow from ::1
# These directories do not require access over HTTP - taken from the original
# phpMyAdmin upstream tarball
#
Order Deny,Allow
Deny from All
Allow from None
Order Deny,Allow
Deny from All
Allow from None
Order Deny,Allow
Deny from All
Allow from None
# This configuration prevents mod_security at phpMyAdmin directories from
# filtering SQL etc. This may break your mod_security implementation.
#
#
#
# SecRuleInheritance Off
#
#

Then we create the system startup links for MySQL and Apache (so that both start automatically whenever the system boots) and start both services:

chkconfig --levels 235 mysqld on
/etc/init.d/mysqld start

chkconfig --levels 235 httpd on
/etc/init.d/httpd start

Create a password for the MySQL user root (replace yourrootsqlpassword with the password you want to use):

mysql_secure_installation

[root@server1 ~]# mysql_secure_installation

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MySQL
SERVERS IN PRODUCTION USE! PLEASE READ EACH STEP CAREFULLY!

In order to log into MySQL to secure it, we'll need the current
password for the root user. If you've just installed MySQL, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.

By default, a MySQL installation has an anonymous user, allowing anyone
to log into MySQL without having to have a user account created for
them. This is intended only for testing, and to make the installation
go a bit smoother. You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n]<-- ENTER ... Success!

Normally, root should only be allowed to connect from 'localhost'. This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n]<-- ENTER ... Success!

By default, MySQL comes with a database named 'test' that anyone can
access. This is also intended only for testing, and should be removed
before moving into a production environment.

As you may have noticed, with the quit; command we have left the MySQL shell and are back on the Linux shell.
BTW, (I'm assuming that the hostname of your ftp server system is server1.example.com) you can access phpMyAdmin under http://server1.example.com/phpMyAdmin/ (you can also use the IP address instead of server1.example.com) in a browser and log in as the user pureftpd. Then you can have a look at the database. Later on you can use phpMyAdmin to administrate your PureFTPd server.

5 Configure PureFTPd

Edit /etc/pure-ftpd/pure-ftpd.conf and make sure that the ChrootEveryone, MySQLConfigFile, and CreateHomeDir lines are enabled and look like this:

The ChrootEveryone setting will make PureFTPd chroot every virtual user in his home directory so he will not be able to browse directories and files outside his home directory. The CreateHomeDir line will make PureFTPd create a user's home directory when the user logs in and the home directory does not exist yet.
Then we edit /etc/pure-ftpd/pureftpd-mysql.conf. It should look like this:

Make sure that you replace the string ftpdpass with the real password for the MySQL user pureftpd in the line MYSQLPassword! Please note that we use md5 as MYSQLCrypt method, which means we will store the users' passwords as an MD5 string in the database which is far more secure than using plain text passwords!
Now we create the system startup links for PureFTPd and start it:

chkconfig --levels 235 pure-ftpd on
/etc/init.d/pure-ftpd start

6 Populate The Database And Test

To populate the database you can use the MySQL shell:

mysql -u root -p

USE pureftpd;

Now we create the user exampleuser with the status 1 (which means his ftp account is active), the password secret (which will be stored encrypted using MySQL's MD5 function), the UID and GID 2001 (use the userid and groupid of the user/group you created at the end of step two!), the home directory /home/www.example.com, an upload and download bandwidth of 100 KB/sec. (kilobytes per second), and a quota of 50 MB:

Now open your FTP client program on your work station (something like WS_FTP or SmartFTP if you are on a Windows system or gFTP on a Linux desktop) and try to connect. As hostname you use server1.example.com (or the IP address of the system), the username is exampleuser, and the password is secret.
If you are able to connect - congratulations! If not, something went wrong.
Now, if you run

ls -l /home

you should see that the directory /home/www.example.com (exampleuser's home directory) has been created automatically, and it is owned by ftpuser and ftpgroup (the user/group we created at the end of step two):

7 Database Administration

For most people it is easier if they have a graphical front-end to MySQL; therefore you can also use phpMyAdmin (in this example under http://server1.example.com/phpMyAdmin/) to administrate the pureftpd database.
Whenever you want to create a new user, you have to create an entry in the table ftpd so I will explain the columns of this table here:

ftpd Table:

Password: The password of the virtual user. Make sure you use MySQL's MD5 function to save the password encrypted as an MD5 string:

UID: The userid of the ftp user you created at the end of step two (e.g. 2001).

GID: The groupid of the ftp group you created at the end of step two (e.g. 2001).

Dir: The home directory of the virtual PureFTPd user (e.g. /home/www.example.com). If it does not exist, it will be created when the new user logs in the first time via FTP. The virtual user will be jailed into this home directory, i.e., he cannot access other directories outside his home directory.

comment: You can enter any comment here (e.g. for your internal administration) here. Normally you leave this field empty.

ipaccess: Enter IP addresses here that are allowed to connect to this FTP account. * means any IP address is allowed to connect.

QuotaSize: Storage space in MB (not KB, as in ULBandwidth and DLBandwidth!) the virtual user is allowed to use on the FTP server. 0 means unlimited.

QuotaFiles: amount of files the virtual user is allowed to save on the FTP server. 0 means unlimited.

8 Anonymous FTP

If you want to create an anonymous ftp account (an ftp account that everybody can login to without a password), you need a user and a group called ftp. Both have been created automatically when you installed the pure-ftpd package, so you don't need to create them manually. However, ftp's homedir is /var/ftp by default, but I'd like to create the anonymous ftp directory in /home/ftp (the normal users' ftp directories are in /home as well, e.g. /home/www.example.com). But of course, you can use the /var/ftp directory for anonymous ftp, if you prefer it.
If you want to use /home/ftp, open /etc/passwd and change the ftp user's homedir from /var/ftp to /home/ftp(don't do this if you want to use /var/ftp):

Then move /var/ftp to /home(don't do this if you want to use /var/ftp):

mv /var/ftp /home

Then we create the directory /home/ftp/incoming which will allow anonymous users to upload files. We will give the /home/ftp/incoming directory permissions of 311 so that users can upload, but not see or download any files in that directory. The /home/ftp directory will have permissions of 555 which allows seeing and downloading of files:

(If you want to use /var/ftp instead, replace /home/ftp with /var/ftp in the above commands.)

Anonymous users will be able to log in, and they will be allowed to download files from /home/ftp, but uploads will be limited to /home/ftp/incoming (and once a file is uploaded into /home/ftp/incoming, it cannot be read nor downloaded from there; the server admin has to move it into /home/ftp first to make it available to others).
Now we have to configure PureFTPd for anonymous ftp. Open /etc/pure-ftpd/pure-ftpd.conf and make sure that you have the following settings in it:

(The AnonymousBandwidth setting is optional - it allows you to limit upload and download bandwidths for anonymous users. 8 means 8 KB/sec. Use any value you like, or comment out the line if you don't want to limit bandwidths.)
Finally, we restart PureFTPd: